Sunday, May 08, 2016

Not entirely, of course, but there is a certain amount of evidence of genetic predisposition to political outlook, especially liberalism vs conservatism. Some of the latest such evidence comes from Genome Wide Association Studies (GWAS). Such studies are useful when you have large sample sizes and traits that are believed for other reasons to be hereditary but controlled by a large number of genes. Height is the classic example. Our adult heights are closely related to those of our parents, but no single gene, nor even small group of genes, can explain the relationship.

The genes we inherit are a mix of those of from our parents, but our inheritance is not randomly assorted, gene by gene. Instead, we inherit chromosomes, each containing thousands of genes, which consist of at most a few chunks from father and a few from mother, so that genes that started out close together on a chromosome are very likely to stay together. GWAS look for variant sections of DNA whose inheritance correlates with inherited traits. For example, if height correlates more with one parent, the GWAS would look for variant sections inherited from that parent. If a trait is governed by many genes, very large sample sizes are necessary for this kind of correlation to have any statistical power. By tradition, an association is considered significant if the odds of it being produces by chance are less than 1/1000 (so-called LOD >= 3), while associations are considered suggestive if LOD >= 2.5. (1/10^2.5 = 1/316).

The disadvantage of such a study is that it can't pinpoint an individual gene, only a region on a chromosome, which may contain dozens or even hundreds of genes, not to mention many more regulatory sequences. Determing how the gene influenced political perspective would be much more difficult.

The news to date is that a GWAS of 13,000 individuals did find regions that reach significance and suggestiveness. The genes can't be determined, but the regions do seem to be rich in genes regulating certain neurotransmitters as well as the sense of smell.

One identifying feature of conservatives is that they don't cope well with new information or environments, so it is at least plausible that this involves some of the neurotransmitters that mediate brain plasticity.